A liquid crystal display device includes a pair of substrates (e.g. glass substrates) between which a liquid crystal display element is sandwiched. Such a liquid crystal display device characteristically has a thin profile, a light weight, and a low power consumption, and is indispensable in everyday life and business as a display of devices such as mobile devices, various monitors, and televisions. Liquid crystal display devices have been widely used in recent years for devices such as electronic books, digital photo frames, industrial appliances (IAs), personal computers (PCs), tablet PCs, and smartphones. For these uses requiring various performances, various liquid crystal display modes have been developed.
Liquid crystal display modes commonly used in recent years are, for example, the vertical alignment (VA) mode which aligns liquid crystal molecules, having negative anisotropy of dielectric constant, vertically to the main faces of the substrates; and the in-plane switching (IPS) mode and the fringe field switching (FFS) mode each of which aligns liquid crystal molecules having positive or negative anisotropy of dielectric constant horizontally to the main faces of the substrates.
For alignment of the liquid crystal molecules, an alignment film is used on which an alignment treatment has been performed by, for example, rubbing or photoalignment treatment. Especially the photoalignment treatment has been noted in these years as a technique for obtaining a liquid crystal display device that provides excellent viewing angle characteristics. The photoalignment treatment is a method of providing alignment controlling force to the alignment film by utilizing a photoactive material as the material of the alignment film, and irradiating the formed film with light such as ultraviolet light. The photoalignment treatment enables control of the alignment directions for the liquid crystal molecules to multiple directions when a voltage is applied, without performing the rubbing treatment to the alignment film, which leads to excellent viewing angle characteristics. Also, the photoalignment treatment also enables contactless alignment treatment on the surface of the alignment film unlike the rubbing treatment, thereby preventing generation of contamination and dirt during the treatment.
Patent Literature 1 and Patent Literature 2 disclose an alignment treatment of generating a uniform alignment controlling force to prevent display failure. Also, Non Patent Literature 1, for example, discloses increasing the degree of alignment of polymers by the post-baking step involved in the process of forming an alignment film.